Constraining the Impact of Bacteria on the Aqueous Atmospheric Chemistry of Small Organic Compounds

In this study, we use a modeling approach to evaluate the potential impact of microbial metabolism on the organic composition of cloud droplets and atmospheric aerosols. Microbial consumption rates for small organic molecules typically found in cloud and aerosol water were incorporated into a 0-D multiphase photochemical atmospheric chemistry model. We then use the model to simulate the evolution of the organic content of individual cloud and aerosol particles, along with the atmospheric gas phase. We find that metabolically active microorganisms may significantly impact organic acid concentrations in the individual aerosols and cloud droplets in which they reside. However, as a result of the low density of metabolically active cells in the atmosphere, the impact of these processes on the chemical composition of the overall population of cloud droplets or aerosols, or on gas-phase chemistry, is likely negligible.